Various systems are known for the capturing of images of objects including live objects. One category of such systems typically utilizes a scanning technology with lasers or other beam emitting sources. The difficulty with systems of this type is that to scan a three-dimensional object, the scan times limit use of the systems to stationary objects.
A second category of image captures systems utilizes triangulated cameras with or without projection of structured light patterns on the object. However, these systems typically are arranged to capture a three-dimensional image of only a portion of the object. Typically such systems also are used only with stationary objects.
It is highly desirable to provide an image capturing system that will capture three-dimensional images of objects that are not stationary, but which may move. It is also desirable that the three-dimensional image has high resolution and high accuracy. It is particularly desirable that the three-dimensional image captures the totality of the object.
It is particularly desirable to provide an image capturing system that will have the ability to capture an accurate three-dimensional image of an infant's head. Capturing of such an image has not been possible with prior image capturing systems for a variety of reasons, one of which being that infants are not stationary for the times that prior systems require to scan or capture the data necessary to produce a three-dimensional image. Another reason is that prior systems could only acquire a partial three-dimensional imager portion. The need for such a system is for producing cranial remodeling bands is great.
Treatment of infants with deformational plagiocephaly with cranial remodeling bands has become a standard of care in the United States. The process by which a cranial remodeling band is fabricated requires obtaining a negative or ‘cast’ impression of the child's head. This is accomplished by first pulling a cotton stockinet over the child's head, and then casting the head with quick setting, low temperature plaster splints.
The casting technique takes approximately 7 to 10 minutes. After the initial casting, a plaster model of the infant's head is made and is used for the fabrication of the cranial remodeling band.
It is highly desirable to simplify the process by utilizing digitization techniques to produce useful digital three-dimensional images of the entire head. We undertook an exhaustive search to identify and evaluate different digitization techniques. Numerous laser scanning, structured light, Moire, and triangulated CCD camera systems were evaluated and rejected as inadequate for one reason or another.
Prior digitization techniques and systems fail to recognize the particular unique challenges and requirements necessary for a system for the digitization of infants. The infant patients to be digitized range in age from three to eighteen months of age. The younger infants are not able to follow verbal instructions and are not able to demonstrate head control while the older infants are difficult to control to more than a brief moment of time. A wide variety of head configurations, skin tone, and hair configurations also needed to be captured. A digitization system must acquire the image in a fraction of a second so that the child would not need to be restrained during image capture, and so that movement during image acquisition would not affect the data. The system data capture must be repeatable, accurate and safe for regular repeated use. In addition, to be used in a clinical setting the system had to be robust, easy to use, and easy to calibrate and maintain without the need for hiring additional technical staff to run the equipment. Image acquisition, processing, and viewing of the data had to be performed in real time in order to ensure that no data was missing before allowing the patient to leave the office.
Numerous existing digitization techniques were evaluated. Laser scanning methods have the disadvantage of the long time, typically 14–20 seconds, that is required to scan an object. Because of the long time, an infant being scanned would have to be restrained in a specific orientation for the scan time. Recent advances in laser scanning have produced scan systems that can perform a scan in 1–2 seconds. However even this scan rate is too slow for an unrestrained infant. The use of lasers also raises concerns regarding their appropriateness and safety for use with an infant population. While many prior digitization systems use ‘eye safe’ lasers, the use of protective goggles is still frequently recommended.
Structured-light Moire and phase-shifted Moire systems used in certain 3D imaging systems are difficult to calibrate, are costly, and are relatively slow and therefore are not suitable for use in obtaining images of infants. In addition these systems are incapable of capturing the entirety of an object in one time instant.
Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) are not particularly useful for the present application simply due to size, expense and concerns regarding radiation and the need to anesthetize the infant.
Prior systems that rely solely on triangulation of digital cameras proved to have insufficient accuracies, particularly as the object being imaged varied in shape and size from a calibration standard.
Structured light systems that combined triangulated digital cameras with a projected grid or line pattern can capture only one surface at a time because the grids projected by multiple projectors interfered with each other resulting in a loss of data. In addition, the images captured by this structured light systems need to be fit together like a three-dimensional jigsaw puzzle, and required that markers be placed on the subject in order to facilitate this registration process.